Kurgan vs Tombstone

Kurgan

name
  • An oblast of Russia in Siberia. 

  • A city, the administrative center of Kurgan Oblast, Russia. Originally called Tsaryovo Gorodishche (Russian Царёво Городи́ще n (Carjóvo Gorodíšče)) (1662-1782). 

Tombstone

name
  • A city in southeastern Arizona. 

How often have the words Kurgan and Tombstone occurred in a corpus of books? (source: Google Ngram Viewer )